Linkage for the day after π day

…although I guess \(\pi+1\) day would be April 14? My site generator doesn’t appear to like putting formulas or markup in article titles; probably that’s a good thing.

• Which sums of roots of unity vanish (\(\mathbb{M}\))? Blog post by Izabella Łaba.

• If, like me, you use LaTeX \newif to keep a single LaTeX source that can compile to either a full paper or its shortened proceedings version, in order to ensure that both versions stay in synch as you edit them, and you find yourself fighting with the LIPIcs proceedings server software, which demands that you avoid conditionals, especially for documentclass, then you might find helpful a quick and dirty Python script that I wrote to strip all the conditionals from LaTeX sources (\(\mathbb{M}\)). Probably someone else has a better (more robust) version of this somewhere but I didn’t find it in some quick searches.

• Tables of Soyga: the first cellular automaton (\(\mathbb{M}\), via)? Somehow I hadn’t previously seen this 2014 post by Anders Sandberg arguing that the Book of Soyga, a 16th-century mystic text owned by John Dee, used cellular automaton based cryptography long before the modern study of cellular automata or cryptography. The Jim Reeds paper deciphering the tables from the Book of Soyga is now a deadlink, but appears likely to be “John Dee and the magic tables in the book of Soyga” (alt. link).

• Logic of graphs (\(\mathbb{M}\)), my latest Wikipedia Good Article. Probably too technical to be of any interest to a general audience, but I think it’s important enough to be worth the effort of covering well despite that.

• Cartographic Treasures of the von Willebrand Collection. Apparently actually a contemporary art installation by Constança Arouca and Madalena Parreira from Portugal? The original post from which I got this has already been deleted.

• Triangles, arcs, and ovals (\(\mathbb{M}\)). Jorn van der Pol on Tuza’s conjecture relating how many disjoint triangles you can find in a graph and how many edge removals it takes to eliminate them all, and on potential matroid generalizations of the conjecture.

• 4sphere asks: How many combinatorially-different Delaunay triangulations can we make with \(n\) points in \(\mathbb{R}^d\)?

• Wired on how Twitter’s new API-access pricing makes it inaccessible to social-network researchers (\(\mathbb{M}\)), who have in the past relied heavily on twitter’s easy access relative to other commercial social media providers.

• Origami and kirigami in the service of science (\(\mathbb{M}\), via). Mostly about how inspiration from paperfolding can be used in the design of flexible devices such as flow-control valves which perform their function passively rather than requiring active control. By Sophie Ramananarivo at the Polytechnic Institute of Paris.

• I discovered today that some important emails sent last month to my campus email address never got there and never showed up in my spam filter (\(\mathbb{M}\)). I strongly suspect overly aggressive campus-level spam filtering. I need to continue keeping that email separate from my gmail to preserve the privacy of student coursework, but I think this means that to the extent possible all mail from off-campus needs to be directed to my gmail. I have updated my contact information page accordingly; if you need to contact me by email for some reason, please adjust your contact information.

• zbMATH rejects a journal, not merely because its most recent issue contained dubious proofs of both the twin prime conjecture and the Riemann hypothesis, but because too many earlier issues were packed with apparently automatically generated papers by apparently automatically generated authors.

• Caitlin Hudon pieces a \(\pi\) quilt with color-coded squares for the first 143 decimal digits of \(\pi\). (The decimal point also occupies a square.)

• TCS aggregator bot for Mastodon.